1. Field of the Invention
This invention pertains generally to dental impression trays and more particularly to an inflatable dental impression tray and tips for use in mixing multi-part dental impression material.
2. Description of Related Art
Many dental procedures require that accurate castings be made of dental surfaces, gums in the case of maxillary casts, or upon a patient presenting an edentulous situation. Traditional dental castings are made by the application by the dental practitioner of one or more layers of a liquid dental impression material to a retention shell called a tray. The liquid dental impression material is highly viscous and quick setting and typically applied as a gel or a mousse. The impression material generally is formed from two constituent components that react when mixed to facilitate quick setting. A dental impression tray loaded with the impression material is inserted into the mouth of a patient and the patient bites down on the material and tray and holding the teeth in that position until the impression material has sufficiently solidified, at which time the tray and dental impression are removed. Once removed from the patient's mouth, the tray with the solidified material contains an impression of the dental surfaces.
Impression trays in current use are typically fabricated from a molded synthetic plastic or resin or from a metal. These impression trays are typically large “U-shaped” devices for taking a full arch impression which spans the entire dental area of the upper or lower jaw, or partial arch trays which are used for taking impressions over a smaller dental areas, such as a quadrant which spans either a left or right half of a full arch (LR, LL, UR, UL). In either case, these shell form trays generally contain some form of inner and outer rigid or semi-rigid sidewall between which the impression material is retained. The trays generally are constructed of sufficient size so that the positioning of the sidewalls accommodates a variety of bite pattern shapes. Due largely to this one size fits all approach, the tray typically requires a large amount of impression material for proper loading.
The elastomeric impression materials currently in use fall within seven major groups. These general groupings include: 1) reversible hydrocolloids; 2) irreversible hydrocolloids such as alginate, 3) addition reaction silicones such as polyvinyl siloxanes; 4) condensation reaction silicones; 5) polyethers; 6) rubber based polysulfides, and 7) light-cured impression materials. A miscellaneous group of impression materials include polyester, wax, silicon, polyacrylics, and putties. Impression materials exhibit varying levels of viscosity and curing times.
A few tray manufacturers have provided anatomical sets of reusable bite trays having a variety of wall heights and spacing, so that a smaller tray may be chosen that has sidewall positions that more accurately reflects the size, shape, and bite pattern of the patient. Yet, in either case, the sidewalls that retain the impression material within the tray can interfere with tissue/bony interfaces, or anomalies, which prevents proper insertion as they often do not properly match the shape of the mouth of the patient. Current dental techniques and devices uniformly teach the use of these shell-like trays into which a two-part impression material is applied before making the dental impression. Various dual-chamber syringes and tubes are used for the dispensing and mixing of the two parts of the impression material. In addition cybernetic mixing units such as Penta™ by ESPE Mix and Mixstar™ by DMG have also been used for mixing and dispensing impression material.
The dental practitioner is required to rapidly load the area within the tray with unsolidified impression material by placing it between the inner and outer impression material retention sidewalls before the impression material begins to solidify. The tray containing the impression material is inserted into the mouth of the patient, adjusted into position, and the patient is directed to bite down and hold their position, so as to get a good impression.
Alternatively the dental practitioner may hold the tray that contains the solidifying impression material in place while the material sets. Due to their size and construction, dental impression trays are comparatively expensive; therefore many impression trays are made to be reusable. Unfortunately, the process of recycling a dental tray requires the removal of all hardened impression material followed by sterilization, which is typically performed within an autoclave. The sterilized tray must then be protected from contamination until reuse. Disposable clam-shell trays have also been manufactured, however, their high unit cost has traditionally been a detractor. Furthermore, in utilizing either disposable or reusable trays, the dental practitioner is required to store an assortment of these trays under antiseptic conditions.
The drawbacks inherent in current tray designs have caused many in the industry to experiment with variations of these standard dental impression trays. Recently, trays have been introduced which include an injection nozzle so that an otherwise typical shell type impression tray can be filled more easily with impression material. The impression material is still retained as in a typical shell arrangement with rigid sidewalls utilized for retention of the impression material.
Other tray varieties have been introduced including trays that contain a plastic or metal perimeter upon which a fabric material is suspended so that a layer of impression material may be built-up on the fabric. However, the principal drawbacks in the use of these practitioner-filled dental impression trays, with their rigid material retention sidewalls, still remains, and the practitioner is left with the choice of using expensive disposable trays, or spending a great deal of time to clean up and recycle used trays.
The task of finding a properly fitting tray with sidewalls compatible with the oral contours of the patient can be inconvenient for the dental practitioner and uncomfortable for the patient. While in addition, the large size of these generic trays requires the use of a substantial quantity of impression material. Furthermore, the practitioner must work quickly to fill all of the tray and to fit the tray properly within the patients mouth before the impression material begins to set. The impression material is formulated to generally provide enough working time to allow this process to be completed, however if filling is accomplished very quickly the patient is left gagging on a mouthful of overflowing aqueous impression material as they wait for the material to harden.
As can be seen, therefore, the development of a dental impression tray that is inexpensive, space efficient, and does not require large imprecise fitting sidewalls to retain the impression material would overcome numerous drawbacks with impression trays currently in use. The inflatable impression tray in accordance with the present invention satisfies that need, as well as others, and overcomes deficiencies in previously known techniques.